As is well known to both commercial and sport sailors, it is frequently desirable that a sailboat have capacity to steer itself, thereby relieving the helmsman for other duties or rest. Such occasions might arise during lengthly ocean passages, when sailing with a shorthanded crew, or, particularly, when sailing single handed. In all such circumstances, it is essential that the self-steering device have complete control of the helm to prevent undesired motion of the sailboat or deviations from a preset course.
Numerous efforts have been made to develop self-steering systems for sailboats, for the general purpose described as well as for other purposes. One category of such mechanisms, for example, has the purpose of maintaining a boat on a given course with a fixed compass heading. As mechanisms in this category generally require auxiliary power responsive to control by some compass device, they are of no interest to the present invention which is specifically directed to a wind powered device designed to hold the boat on a selected heading or course relative to the apparent wind direction.
In the particular category of self-steering mechanisms for sport sailboats, some fairly effective and reliable systems have been developed in the past decade for achieving self-steering relative to the apparent wind direction. Such systems generally employ a wind vane to measure the apparent wind direction, and use the wind pressure on the wind vane, when the sailboat wonders off course, to drive a steering device that will steer the boat back to the desired course. In such systems, the steering device can be a sailboat's tiller, an auxiliary rudder or trim tab, a servo blade for amplifying power, or like means, depending upon the particular system used. Self-steering mechanisms of this general type, wherein wind vanes are employed to sense apparent wind direction, are disclosed in Gianoli U.S. Pat. Nos. 3,180,298 and 3,319,594, Ross-Clunis U.S. Pat. No. 3,678,878, Smith U.S. Pat. No. 3,942,461 and Saye U.S. Pat. No. 3,765,361.
Although effective to a degree, known self-steering mechanisms of the type described have not proved to be entirely satisfactory in use.
Wind vane units which pivot about an axis in response to changes in the direction of apparent wind wherein such axis is tiltable in a vertical plane with respect to the sailboat have been employed for purposes of varying the sensitivity of the wind vane. Assuming a wind vane is normally in a vertical position and pivots about a horizontal axis, it is known to decrease the effective leverage and power of the wind vane by tilting its axis out of a horizontal disposition so as for example to better operate in various types of wind and sea conditions. However, in order to convert angular vane deflections into linear movement for actuating an auxiliary rudder means, it has been necessary to employ rather cumbersome mechanical linkage when it is desired to utilize a vane having a tiltable axis.
In addition, it has been known to utilize a transmission intermediately disposed between a wind vane having a non-tiltable axis and an auxiliary rudder so as to vary the ratio therebetween. It has not been considered in the prior art to incorporate the advantages of a wind vane having a tiltable axis into a self-steering device having the advantages of a variable transmission means wherein the transmission means ratio could be adjusted independently of the wind vane axis tilt.
Lastly, it is known in the prior art to utilize an auxiliary rudder pivoted about a pendulum means wherein the latter is pivoted about an axis normal to the auxiliary rudder axis. In such an arrangement, vane movements are transmitted to the auxiliary rudder whereby the force of water flow past the deflected auxiliary rudder causes the pendulum to swing. Movement of the pendulum is transmitted by lines, cable or similar mechanisms to the main rudder of the boat in such a way as to cause the main rudder to correct the sailboat's heading relative to the wind. In such a structure, as set forth in applicant's aforesaid British patent, a gearing mechanism is employed to reduce the angle of the auxiliary rudder blade to water flow as the pendulum swings so as to provide a reducing force on the pendulum as it continues to swing. However, this structure necessitates the relatively more complex nature of the gearing referred to whereas the structure as set forth and claimed in the present invention eliminates the need for such gearing while still providing for reduction in the angle of incidence of the auxiliary rudder blade to water flow as the associated pendulum swings through the water.